"The challenging part was never the work, that was never it. It was sort of the in-between work. The social aspects outside of it," he revealed to Grylls. "Everywhere you go to a certain extent, there is press in some form. Whether you're going out to an event where you're supposed to be out with your friends, there will be press there. If you're leaving your house to go to the grocery store, there will be press there. It can be confusing."

"You spend a lot of time in your house, going crazy," he continued. "Pretty soon, you need a social lubricant, you know? Once I needed that, it became [I needed it] to go anywhere. It was getting to the point where I was caring less about the work and waiting more for the weekend, where I couldn't wait to go out and let loose and have fun. But then, when Monday and Tuesday were difficult to get through, I was like, 'This is bad,'" Efron explained.

The actor previously spoke out about his battle with alcohol to the Hollywood Reporter, acknowledging that he "was drinking a lot, way too much," and reportedly claimed that he had been using drugs as well, which many think to have been cocaine.

Fortunately, Efron knew he needed to get help -- and time in rehab seemed to change his perspective on things, for the better.

"I just really never again want to take anything from the outside into me to feel good about my outside," he said. You can watch him open up to Bear Grylls about his battle with addiction here.